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Mitochondria can be thought of as cellular "power plants," converting the chemical energy in food into available energy for the cell in the form of adenosine triphosphate, or ATP, through the process of oxidative phosphorylation. Many cells do not contain mitochondria, however, and find alternate ways to obtain the energy they require.

All Bacteria Lack Mitochondria

No bacteria contain mitochondria. In fact, according to Rice University, the endosymbiotic hypothesis proposes that mitochondria are actually the descendants of ancient bacteria that were engulfed by other cells and lost their ability to function outside their new hosts. Bacteria instead generate energy through different types of oxidation such as respiration, in which oxygen serves as the final electron acceptor, and fermentation, in which another organic compound fills that role.

Eukaryotic Exceptions

Most eukaryotic cells -- those that contain nuclei -- also contain mitochondria, but there are exceptions to this rule. Some parasitic protists, for example, take energy from their hosts and do not have mitochondria, as explained by an article in the Journal of Eukaryotic Microbiology. In humans, mature red blood cells, or erythrocytes, lack mitochondria as well, as reported by the Encyclopedia Britannica.

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About the Author

Daniel Walton is a Cincinnati-based science writer whose articles have appeared on the blog Sword of Science and the Internet science hub Real Clear Science. He holds a Master of Science in crop science from the University of Illinois and grows a substantial vegetable garden in his backyard.